Human-caused global changes in ecological drivers, such as carbon dioxide concentrations, climate, and nitrogen deposition, as well as direct human impacts (land use change, species movements and extinctions, etc.) are increasingly recognized as key to understanding contemporary ecosystem dynamics, but a coherent theory of ecological responses to global change has not yet been developed. There are four attributes that characterize phenomena considered under global change (the direct and indirect effects of human actions) that collectively present unique challenges to existing theories. Two of these attributes occur under current conditions: (1) there is natural variation in environmental drivers and system responses within a hierarchy of interacting spatial and temporal scales, and (2) drivers and processes interact across scales such that spatial context and connectivity among spatial units are important to system dynamics; the other two attributes are unique to systems undergoing global change: (3) by definition, global change drivers have an anthropogenic origin that in many cases act outside the realm of natural selection, and (4) these drivers are changing in magnitude, frequency, and direction that result in trajectories of responses that differ from those studied in the past, and are often characterized by threshold behavior and regime shifts. We outline the characteristics of a theory of global change based on propositions derived from the four system attributes, and that draws upon existing theories from a range of sub-disciplines of ecology and other disciplines. This interacting scale theory has the potential to integrate much of our information about global change drivers and responses.